LATCH CIRCUIT AND FLIP-FLOP CIRCUIT
A latch circuit includes: first nodes which are three or more and to which a voltage in a first signal level is set; second nodes which are three or more and to which a voltage in a second signal level obtained by inverting the first signal level is set; and first node voltage control circuits having the first nodes; and second node voltage control circuits having the second nodes. Each of the first node voltage control circuits is connected with at least two of the three or more second nodes, and controls the voltage of the first node based on the voltages of the at least two second modes. Each of the second node voltage control circuits is connected with at least two of the three or more first nodes and controls the voltage of the second node based on the voltages of the at least two first nodes.
Latest NEC ELECTRONICS CORPORATION Patents:
- INDUCTOR ELEMENT, INDUCTOR ELEMENT MANUFACTURING METHOD, AND SEMICONDUCTOR DEVICE WITH INDUCTOR ELEMENT MOUNTED THEREON
- Differential amplifier
- LAYOUT OF MEMORY CELLS AND INPUT/OUTPUT CIRCUITRY IN A SEMICONDUCTOR MEMORY DEVICE
- SEMICONDUCTOR DEVICE HAVING SILICON-DIFFUSED METAL WIRING LAYER AND ITS MANUFACTURING METHOD
- SEMICONDUCTOR INTEGRATED CIRCUIT DESIGN APPARATUS, DATA PROCESSING METHOD THEREOF, AND CONTROL PROGRAM THEREOF
This patent application claims priority on convention based on Japanese Patent Application No. 2007-291060. The disclosure thereof is incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a latch circuit and a flip-flop circuit that uses it.
2. Description of Related Art
In recent years, it is known that a soft error is caused by high-energy radiation (alpha ray and neutron beam) irradiating the latch circuit. The soft error is a failure caused by “singe-event upset (SEU)” in which data is inverted, resulting from a phenomenon that alpha rays and/or neutron beams are incident on the latch circuit to generate electric charges and the electric charges are collected by a region (node) for retaining the data. The soft error is a transient failure, and if correct data can be rewritten anew, the latch circuit will operate normally again. However, even if it is temporary, since the stored data is inverted, there is a case that its influence takes effect in the whole computer system.
The soft error occurring in a conventional latch circuit shown in
A case where collection of electric charges occurs in a state that the node N10A is set to “1” (high level) and the node N20B is set to “0” (low level) will be described. In an initial stage, since a voltage in the node N10A is in the high level, a P-channel type MOS transistor MP10B is maintained in an ON state, and an N-channel type MOS transistor MN10B is maintained in the OFF state. Moreover, since a voltage in the node N20B is in the low level, a P-channel type MOS transistor MP10A is maintained in an OFF state, and an N-channel type MOS transistor MN10A is maintained in the ON state. Here, if radiation is allowed to be incident on near the node N10A, electrons are collected in the node N10A, so that the data set to the node N10A is inverted from “1” to “0” (the node N10A changes from the high level to the low level). At this time, since gate voltages of the P-channel type MOS transistor MP10B and the N-channel type MOS transistor MN10B change to the low level, the P-channel type MOS transistor MP10B changes from the OFF state to the ON state, and the N-channel type MOS transistor MN10B changes from the ON state to the OFF state. Thereby, a voltage of the node N20B changes to the high level. That is, the data set to the node N20B is inverted from “0” to “1.” Thus, the latch circuit shown in
As a semiconductor memory device that is hardened against such a soft error, a DICE (Dual Interlocked Cell) is known.
The DICE is provided with nodes N10A and N10C at which data of a same signal level are set, and nodes N20B and N20D at which inverted data of the above data set to the nodes N10A, N10C are set. For example, when the nodes N10A and N10C are set to the data “1,” the nodes N20B and N20D are set to the data “0.” In this case, since the voltages in the nodes N10A and N10C are in the high level, the P-channel type MOS transistors MP10B and MP10D are maintained in the OFF state, and the N-channel type MOS transistors MN10B and MN10D are maintained in the ON state. Moreover, since the voltages in the nodes N20B and N20D are in the low level, the P-channel type MOS transistors MP10A and MP10C are maintained in the ON state, and the N-channel type MOS transistors MN10A and MN10C are maintained in the OFF state.
Here, if radiation is incident near the node N10A, electric charges will be collected in the node N10A, and the data set to the node N10A will be inverted from “1” to “0” (transition from the high level to the low level). At this time, since gate voltages of the P-channel type MOS transistor MP10B and the N-channel type MOS transistor MN10D change to the low level, the P-channel type MOS transistor MP10B changes from the OFF state to the ON state, and the N-channel type MOS transistor MN10D changes from the ON state to the OFF state. On the other hand, at this time, the N-channel type MOS transistor MN10B and the P-channel type MOS transistor MP10D are still in the ON state and in the OFF state, respectively. Therefore, the voltages of the nodes N20B and N20D change from the low level to an unstable level (indeterminate value) that is neither the low level nor the high level. This voltage change propagates to the P-channel type MOS transistor MP10C and the N-channel type MOS transistor MN10C, and also affects a voltage of the node N10C after a predetermined time. However, since it takes a certain time until the voltage of the node N10C is stabilized, during that time the node N10C can maintain the high-level voltage. That is, even if the data “1” of the node N10A is inverted to data “0.” the node N10C continues to hold the data “1” for a while. If charge collection in the node N10A ends during this time, the voltage of each node can return by the voltage maintained in the node N10C. Thus, in the DICE, since the soft error is suppressed even if the charge collection occurs in a single node, a soft error rate of the latch circuit can be reduced.
Moreover, as another example, a technique of improving the soft error rate of the latch circuit is described in Japanese Patent Application Publication (JP-P2006-129477A: related art 1). A semiconductor circuit described in the related art 1 is provided with two inverters, each of whose output and input are connected for feed back and when an input of the one inverter suffers a failure by charge collection, the inverter is made to be in a tristate or in a high impedance state by a control signal, whereby the soft error rate is improved.
In recent years, a problem has been pointed out, of charge sharing that electric charges generated by one time of incidence of radiation are collected by two or more nodes. The problem of charge sharing will be described in “Single Event Upsets in a 130 nm Hardened Latch Design Due to Charge Sharing” by 0. Amusan, et al. (45th Annual International Reliability Physics Symposium, IEEE Proceedings, United States, 2007, pp. 306-311) as a related art 2, and “Assessing the impact of scaling on the efficacy of spatial redundancy based SER mitigation schemes for terrestrial applications” by N. Seifert et al. (IEEE Workshop on Silicon Errors in Logic-System Effects, United States, 2007, which was searched on Oct. 23, 2007, on the Internet (URL: http://www.seise.org/selse07.program.linked.htm)) as a related art 3. Although the DICE shown in
For example, in the above example, when the charge collection has occurred in the two nodes N10A and N10C simultaneously, the P-channel type MOS transistors MP10B and MP10D change from the OFF state to the ON state almost simultaneously, and the N-channel type MOS transistors MN10B and MN10D change from the ON state to the OFF state almost simultaneously. In this case, similarly with the principle described above, not only the nodes N10A and N10C, on which radiation has been incident, but also the nodes N20B and N20D, on which no radiation has been incident, invert their values immediately. For this reason, also, in the whole DICE, it will be stabilized in a state that the latched data is inverted.
Similarly to a technique described in the related art 1, there is a case that, when the charge collection has occurred in a plurality of nodes, the soft error cannot be suppressed depending on the positions of the charge collection.
As described above, in the conventional technique, it is impossible to suppress the soft error when a plurality of memory nodes collected the electric charges by charge sharing. For this reason, further improvement of a rate of the soft error occurring in the latch circuit is demanded.
SUMMARYIn an aspect of the present invention, a latch circuit includes: first nodes which are three or more and to which a voltage in a first signal level is set; second nodes which are three or more and to which a voltage in a second signal level obtained by inverting the first signal level is set; and first node voltage control circuits having the first nodes; and second node voltage control circuits having the second nodes. Each of the first node voltage control circuits is connected with at least two of the three or more second nodes, and controls the voltage of the first node based on the voltages of the at least two second modes. Each of the second node voltage control circuits is connected with at least two of the three or more first nodes and controls the voltage of the second node based on the voltages of the at least two first nodes.
In another aspect of the present invention, a flip-flop circuit includes: two latch circuits; and a clock signal generating circuit configured to supply the two latch circuits. Each of the latch circuit includes: first nodes which are three or more and to which a voltage in a first signal level is set; second nodes which are three or more and to which a voltage in a second signal level obtained by inverting the first signal level is set; and first node voltage control circuits having the first nodes; and second node voltage control circuits having the second nodes. Each of the first node voltage control circuits is connected with at least two of the three or more second nodes, and controls the voltage of the first node based on the voltages of the at least two second modes. Each of the second node voltage control circuits is connected with at least two of the three or more first nodes and controls the voltage of the second node based on the voltages of the at least two first nodes. One of the two latch circuits function as a latch circuit on an input side in which data is supplied to the second node through the transfer gates and the other functions as the latch circuit on an output side in which the data latched in the first node is outputted. The first node of the latch circuit on the input side is connected with the second node of the latch circuit on the output side through the transfer gate in the latch circuit on the output side.
According to the present invention, it is possible to reduce a rate of soft error in the latch circuit. Moreover, it is possible to suppress an occurrence of soft error resulting from the charge sharing in the latch circuit.
The above and other objects, advantages and features of the present invention will be more apparent from the following description of certain embodiments taken in conjunction with the accompanying drawings, in which:
Hereinafter, a latch circuit according to the present invention will be described with reference to the attached drawings. In the drawings, the same or similar reference numerals designate the same or similar components, respectively.
First EmbodimentMoreover, the latch circuit in the first embodiment has the data holding nodes and is provided with node voltage control circuits 1A, 1B, 1C, 1D, 1E, 1F, and 1G for controlling voltages of the data holding nodes.
Each of the node voltage control circuits 1A, 1C, 1E, and 1G includes a P-channel type MOS transistor and an N-channel type MOS transistor whose drains are connected through a corresponding one of the nodes N1A, N1C, N1E, and N1G. Moreover, each of the node voltage control circuits 1A, 1C, 1E, and 1G is provided with a transistor that is connected in series through the drain and the source between the power supply and the transistor connected to the node N1A, N1C, N1E, or N1G. The gates of the plurality of transistors that are connected in series between the each of the nodes and the power supply are connected to different ones of the nodes N2B, N2D, N2F, and N2H, respectively.
For example, the node voltage control circuit 1A is provided with a P-channel type MOS transistor MP1A and an N-channel type MOS transistor MN1A whose drains are connected through the node N1A. The node voltage control circuit 1A is further provided with a P-channel type MOS transistor MP2A that is connected in series between a source of the P-channel type MOS transistor MP1A and a first power supply (VDD), and an N-channel type MOS transistor MN2A that is connected in series between the source of the N-channel type MOS transistor MN1A and a second power supply (GND). The gates of the P-channel type MOS transistors MP1A and MP2A and the N-channel type MOS transistors MN1A and MN2A are connected to different ones of the nodes N2B, N2D, N2F, and N2H, respectively. In an example shown in
Each of the node voltage control circuits 1B, 1D, 1F, and 1H is provided with the P-channel type MOS transistor and the N-channel type MOS transistor whose drains are connected through a corresponding one of the nodes N2B, N2D, N2F, and N2H. Moreover, each of the node voltage control circuits 1B, 1D, 1F, and 1H is provided with a transistor that is connected in series between the power supply and the transistor connected to the corresponding one of the nodes N2B, N2D, N2F, and N2H. The gates of a plurality of the transistors connected in series between the node and the power supply are connected to different nodes of the nodes N1A, N1C, N1E, and N1G, respectively. For example, the node voltage control circuit 1B is provided with a P-channel type MOS transistor MP1B and an N-channel type MOS transistor MN1B whose drains are connected through the node 2B. The node voltage control circuit 1B is provided with a P-channel type MOS transistor MP2B that is connected in series between the source of the P-channel type MOS transistor MP1B and the first power supply (VDD), and an N-channel type MOS transistor MN2B that is connected in series between the source of the N-channel type MOS transistor MN1B and the second power supply (GND). The gates of the P-channel type MOS transistors MP1B and MP2B and the N-channel type MOS transistors MN1B and MN2B are connected to different ones of the nodes N1A, N1C, N1E, and N1G, respectively. In an example shown in
Here, in the example shown in
Node N1A: MP1B, MN1D, MP2F, MN2H
Node N1C: MN1B, MP1D, MN2F, MP2H
Node N1E: MP2B, MN2D, MP1F, MN1H
Node N1G: MN2B, MP2D, MN1F, MP1H
Node N2B: MN1A, MP1C, MN2E, MP2G
Node N2D: MP1A, MN1C, MP2E, MN2G
Node N2F: MN2A, MP2C, MN1E, MP1G
Node N2H: MP2A, MN2C, MP1E, MN1G
In this way, one transistor is selected from each of the node voltage control circuits 1B, 1D, 1F, and 1H that control voltages of the nodes N2B, N2D, N2F, and N2H as the second nodes, and is connected to a corresponding one of the nodes N1A, N1C, N1E, and N1G as the first nodes. Similarly, one transistor is selected from each of the node voltage control circuits 1A, 1C, 1E, and 1G that control the voltages of the nodes N1A, N1C, N1E, and N1G, and is connected to a corresponding one of the nodes N2B, N2D, N2F, and N2H. Moreover, as shown in
By the above configuration, the semiconductor memory device according to the present invention can hold a data in the nodes N1A, N1C, N1E, and N1G, and can hold the inverted data of the data in the nodes N2B, N2D, N2F, and N2H.
Next, referring to
An operation when an N type diffusion layer contained in the node NIA collects electrons by incidence of radiation, and the held data is inverted from “1” to “0” temporarily will be described. In this case, since the signal level of the node N1A changes to the low level, the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state, and the N-channel type MOS transistors MN1D and MN2H change from the ON state to the OFF state. Since by this change, the nodes N2D and N2H are disconnected from the first power supply (VDD) and the second power supply (GND), they change from a voltage in the low level to an intermediate voltage. On the other hand, the nodes N2B and N2F are disconnected from the first power supply (VDD) by the P-channel type MOS transistors MP2B and MP1F, and are maintained to be connected to the second power supply (GND) by the N-channel type MOS transistors MN1B and MN2B and the N-channel type MOS transistors MN1F and MN2F. For this reason, even if the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state, the nodes N2B and N2F continue to maintain the low level. As a result, the levels of the nodes N2D and N2H become temporarily unstable. This voltage variation propagates as a noise signal to transistors whose gates connected to the nodes N2D and N2H and also affects voltages of other nodes. However, it takes a predetermined time until the voltage variation of the nodes N2D and N2H affects the other nodes, and during that time, the other nodes maintain original correct levels. If the charge collection in the node N1A ends during this time, the voltage values of the nodes N1A, N2D, and N2H will return to states before the charge collection by the voltages maintained in the nodes N1B, N1C, N1E, N2F, and N1G.
Moreover, in the present invention, the voltage variations in the nodes N2B, N2D, N2F, and N2H are suppressed by transistors connected to the nodes with a less voltage variation. In detail, although the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state, the P-channel type MOS transistors MP2B and MP1F connected to the node N1E maintains the OFF state. For this reason, the P-channel type MOS transistors MP2B and MP1F function to suppress the voltage variations in the nodes N2B and N2F described above and to make the nodes N2B and N2F maintain the low level. Similarly, although the N-channel type MOS transistors MN1D and MN2H change from the ON state to the OFF state, the N-channel type MOS transistors MN2D and MN1H connected to the node N1E maintain the ON state. For this reason, the N-channel type MOS transistors MN2D and MN1H function to suppress the voltage variations in the nodes N2D and N2H described above. In detail, the voltage in the data holding node is determined based on a ratio of impedance of the P-channel type MOS transistor side and impedance of the N-channel type MOS transistor side in the node voltage control circuit to which the node belongs. Since the nodes N2D and N2H are disconnected from the second power supply (GND) by the N-channel type MOS transistors MN1D and MN2H, they cannot maintain a perfect low level. However, since the N-channel type MOS transistors MN2D and MN1H maintain the ON state, a variation of the above-mentioned impedance ratio is small, and the voltage variations in the nodes N2D and N2H are suppressed. From the above, the data having been set in the nodes N2B, N2D, N2F, and N2H become hard to vary, and the holding times of the data “1” in the nodes N1C, N1E, and N1G increase. Alternatively, the nodes N2B, N2D, N2F, and N2H maintain the data “0,” and the data “1” having been set in the nodes N1C, N1E, and N1G become hard to be inverted. For this reason, an occurrence of a soft error in the latch circuit 10 is further suppressed compared with before.
In this way, in the present invention, a plurality of transistors are connected in series between the power supply and the data holding nodes and each of their gates is connected to a different data holding node. Therefore, the voltage variation in the data holding nodes can be suppressed, so that inversion of data is prevented
<2> When Charge Collection Occurs in Two Data Holding Nodes (Case 1)An operation when N type diffusion layers contained in the nodes N1A and N1E collect electrons simultaneously by incidence of radiation and the both nodes are inverted from the data “1” to the data “0” simultaneously will be described. In this case, since the signal level of the node N1A changes to the low level, the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state and the N-channel type MOS transistors MN1D and MN2H change from the ON state to the OFF state. Moreover, since a signal level of the node N1E changes to the low level, the P-channel type MOS transistors MP2B and MP1F change from the OFF state to the ON state, and the N-channel type MOS transistors MN2D and MN1H change from the ON state to the OFF state. That is, all the P-channel type MOS transistors MP1B, MP2B, MP1D, MP2D, MP1F, MP2F, MP1H, and MP2H in the node voltage control circuits 1B, 1D, 1F, and 1H change in a switching state. Accordingly, the voltages of the nodes N2B, N2D, N2F, and N2H change from the low level to an intermediate level.
This voltage variation propagates as noise signals to transistors whose gates are connected to the nodes N2B, N2D, N2F, and N2H and affect the voltages in the nodes N1C and N1G. However, variation speeds of the voltages of the nodes N1C and N1G are moderate, compared with the nodes N2B, N2D, N2F, and N2H, and the voltage values maintain the high level for a predetermined period. That is, even when the data “1” of the node N1A in which charge collection has occurred is inverted to “0,” the nodes N1C and N1G maintain the data “1” for a while. If the charge collection in the nodes N1A and N1E ends during this time, the voltage of the each node returns to a state before the charge collection based on the voltages maintained in the nodes N1C and N1G.
In this way, according to the present invention, even when the charge collection has occurred simultaneously in two data holding nodes, it is possible to prevent generation of the soft error Mover, in this example, even when either conductive type of the transistors that control the data holding nodes changes its switching state in each of the transistor control circuits N2B, N2D, N2F, and N2H, the generation of the soft error can be suppressed.
<3> When Charge Collection Occurs in Two Data Holding Nodes (Case 2)An operation of a case that N type diffusion layers contained in the nodes N1A and N1C collect electrons simultaneously in response to incidence of radiation and the both of the nodes invert from a data “1” to a data “0” will be described. In this case, since the signal level of the node N1A changes to the low level, the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state, and the N-channel type MOS transistors MN1D and MN2H change from the ON state to the OFF state. Moreover, since a signal level of the node N1C changes to the low level, the P-channel type MOS transistors MP1D and MP2H change from the OFF state to the ON state, and the N-channel type MOS transistors MN1B and MN2F change from the ON state to the OFF state. That is, switching states change in following transistors: the P-channel type MOS transistor MP1B and the N-channel type MOS transistor MN1B of the node voltage control circuit 1B, the P-channel type MOS transistor MP1D and the N-channel type MOS transistor MN1D of the node voltage control circuit 1D, the P-channel type MOS transistor MP2F and the N-channel type MOS transistor MN2F of the node voltage control circuit 1F, and the P-channel type MOS transistor MP2H and the N-channel type MOS transistor MN2H of the node voltage control circuit 1H. Thereby, the voltages of the nodes N2B, N2D, N2F, and N2H change from the low level to the intermediate level.
This voltage variation, as described above, propagates as a noise signal to the transistors whose gates connected to the nodes N2B, N2D, N2F, and N2H, and also affects the voltages of the nodes N1E and N1G. However, the variation speeds of the voltages of the nodes N1B and N1G are moderate, compared with the nodes N2B, N2D, N2F, and N2H, and the voltages maintain the high level for a predetermined time. That is, even if the data “1” of the nodes N1A and N1C in which the charge collection has occurred are inverted to the data “0,” the nodes N1E and N1G continue to maintain the data “1” for a while. If the charge collection in the nodes N1A and N1C ends during this time, voltage values of the nodes N1A and N1C whose data are inverted and a voltage value of the data holding node set to the indeterminate level return to states before the charge collection based on voltages maintained in the nodes N1E and N1G.
Moreover, similarly to the case that the single data holding node collects electric charges, the voltage variation in the nodes N2B, N2D, N2F, and N2H are suppressed by the P-channel type MOS transistors MP2B and MP1F and the N-channel type MOS transistors MN1D and MN2H that are connected to the node N1E having a small voltage variation, and the P-channel type MOS transistors MP2D and MP1H and the N-channel type MOS transistors MN2B and MN1F connected to the node N1G. For this reason, the data having been set to the nodes N2B, N2D, N2F, and N2H become resistant to take indeterminate values, and the holding time of data “1” in the nodes N1C, N1E, and N1G increase. Otherwise, the nodes N2B, N2D, N2F, and N2H maintain the data “0,” and the data “1” of the nodes N1C, N1E, and N1G are not inverted.
In this way, in this example, even when two transistors of different conduction types change the switching state among transistors for controlling the data holding nodes in each of the transistor control circuits N2B, N2D, N2F, and N2H, the generation of the soft error can be suppressed.
Referring to
Referring to
Referring to
As described above, according to the present invention, even if the charge collection has occurred in two nodes by charge sharing, the generation of the soft error can be suppressed (there is no occurrence of the soft error actually). It should be noted that even when a combination of two data holding nodes for collecting electric charges is different from the example shown in the above, the generation of the soft error can be suppressed similarly.
<4> When the Charge Collection Occurs in Three Data Holding NodesN type diffusion layers contained in the nodes N1A, N1C, and N1E may collect electrons simultaneously by incidence of radiation and the both nodes may be inverted from the data “1” to the data “0” simultaneously. An operation of such a case will be described. In this case, since the signal level of the node N1A changes to the low level, the P-channel type MOS transistors MP1B and MP2F change from the OFF state to the ON state and the N-channel type MOS transistors MN1D and MN2H change from the ON state to the OFF state. Moreover, since the signal level of the node N1C changes to the low level, the P-channel type MOS transistors MP1D and MP2H change from the OFF state to the ON state and the N-channel type MOS transistors MN1B and MN2F change from the ON state to the OFF state. Further, since the signal level of the node N1E changes to the low level, the P-channel type MOS transistors MP2B and MP1F change from the OFF state to the ON state and the N-channel type MOS transistors MN2D and MN1H change from the ON state to the OFF state. That is, switching states change in the following transistors: the P-channel type MOS transistors MP1B and MP2B and the N-channel type MOS transistor MN1B of the node voltage control circuit 1B, the P-channel type MOS transistor MP1D and the N-channel type MOS transistors MN1D and MP2D of the node voltage control circuit 1D, the P-channel type MOS transistors MP1F and MP2F and the N-channel type MOS transistor MN2F of the node voltage control circuit 1F, and the P-channel type MOS transistor MP2H and the N-channel type MOS transistors MN1H and MN2H of the node voltage control circuit 1H. Thereby, the voltages of the nodes N2B, N2D, N2F, and N2H change from the low level to an intermediate level.
This voltage variation propagates as a noise signal to transistors whose gates are connected to the nodes N2B, N2D, N2F, and N2H, as described above, and also affects the voltage of the node N1G. However, the variation speed of the voltage of the node N1G is moderate, compared with the nodes N2B, N2D, N2F, and N2H, and the voltage of the node N1G maintains the high level. That is, even if the data “1” of the nodes N1A, N1C, and N1E in which the charge collection has occurred is inverted to the data “0,” the node N1G maintains the data “1” for a while. If the charge collection in the nodes N1A, N1C, and N1E ends during this time, the voltage values of the data holding nodes N1A, N1C, and N1E whose data are inverted and the voltage value of the data holding node whose voltage has been an indeterminate value return to the states before the charge collection by the voltage maintained in the node N1G.
As described above, according to the present invention, even if the charge collection has occurred in two nodes by charge sharing, the generation of the soft error can be suppressed. It should be noted that even if a combination of three data holding nodes that collect the electric charges is different from the example shown above, it is possible to suppress the occurrence of the soft error similarly.
Second EmbodimentThe latch circuit 10 shown in
Since the transistors with smaller influence of the noise signal are removed in the latch circuit 10 shown in
Moreover, any one of the node voltage control circuits 1A to 1H may be reduced from the latch circuit 10 shown in
Since in the latch circuit 10 shown in
Further, the node voltage control circuits 1A to 1H (gates of the P-channel type MOS transistors MP1A to MN2H) to which the nodes N1A to N214 are connected are not restricted to the form shown in
Here, a connection relationship between the data holding nodes in the latch circuit 10 shown in
Node N1A: MP1B, MP2D, MN2F, MN1H
Node N1C: MN1B, MP1D, MP1F, MN2H
Node N1E: MN2B, MN1D, MP1F, MP2H
Node N1G: MP2B, MN2D, MN1F, MP1H
Node N2B: MN1A, MP1C, MP2E, MN2G
Node N2D: MN2A, MN1C, MP1E, MP2G
Node N2F: MP2A, MN2C, MN1E, MP1G
Node N2H: MP2A, MP2C, MN2E, MN1G
Also, in the latch circuit 10 shown in
A semiconductor memory device shown in
It should be noted that a combination of the data holding node and the gate of the transistor connected to the data holding node can be arbitrarily set up ever, in the form where the node voltage control circuit or the transistor in the node voltage control circuit is reduced.
As one of indices that are used frequently as an index of the easiness of generation of the soft error, critical charge (critical amount of electric charge) is known. The critical charge is a numerical value of a quantity of electric charges at which a data of a specific data holding node being latched is inverted and not returned when electric charges are injected to the data holding node by incidence of radiation, thereby causing the soft error. When this numerical value becomes larger, the soft error will become slower to occur. In order to check the effect of the present invention, the inventor obtained an example of the critical charge through simulation when the electric charges are injected into a plurality of nodes simultaneously by a process of the 90-nm generation. It should be noted that a distribution ratio of electric charges injected to the nodes may differ depending on an incident position and an incident angle of radiation. Here, for simplification, the simulation is performed under the assumption that a same quantity of electric charges is injected to the each data holding node.
In the latch circuit shown in
On the other hand, as a result of performing a simulation similarly in the latch circuit 10 shown in
The semiconductor memory device described above is applicable to a flip-flop circuit.
A configuration of the flip-flop circuit that uses the semiconductor memory device according to the present invention will be described referring to
Referring to
The latch circuits 10-1 and 10-2 have the configuration in which clocked transistors CMP11, CMP12, CMP13, CMP14, CMN11, CMN12, CMN13, and CMN14 are added to the latch circuit 10 shown in
Clock signals CKBA, CKBB, CKTA, CKTB, CKBC, CKBD, CKTC, and CKTD are respectively supplied to the gates of the clocked transistors CMP11, CMP12, CMP13, CMP14, CMN11, CMN12, CMN13, and CMN14 in a latch circuit 10-1. Similarly, clock signals CKTA, CKTB, CKBA, CKBB, CKTC, CKTD, CKBC, and CKBD are respectively supplied to the gates of the clocked transistors CMP11, CMP12, CMP13, CMP14, CMN11, CMN12, CMN13, and CMN14 in a latch circuit 10-2. The clock signals are generated by the clock signal generating circuit 40 shown in
The transfer gate circuit 20-1 is provided with a plurality of transfer gates to which data signal DATA is supplied. Outputs of the plurality of transfer gates are connected to input-side nodes N2B, N2D, N2F, and N2G in the latch circuit 10-1. The data signal DATA is outputted to the nodes N2B, N2D, N2F, and N2G according to the clock signals CKBA, CKBB, CKTA, CKTB, CKBC, CKBD, CKTC, and CKTD.
The transfer gate circuit 20-2 is provided with a plurality of transfer gates to be connected to the output-side nodes N1A, N1C, N1E, and N1G in the latch circuit 10-1. The plurality of transfer gates output the data signal DATA supplied from the nodes N1A, N1C, N1E, and N1G of the latch circuit 10-1 to the input-side nodes N2B, N2D, N2F, and N2G of the latch circuit 10-2 according to the clock signals CKBA, CKBB, CKTA, CKTB, CKBC, CKBD, CKTC, and CKTD.
The output circuit 30 is provided with transistors whose gates are connected to the output-side nodes N2A, N2C, N2E, and N2G of the latch circuit 10-2.
With the above configuration, the flip-flop circuit shown in
As described above, the present invention has been described in detail. Specific configurations are not restricted to the above-mentioned embodiments, and even if modifications that do not deviate from a gist of the present invention are given to the embodiment, they are included in the present invention. In the present embodiment, the example that the latch circuit was applied to the flip-flop has been shown. However, application is not restricted to this, for example, and the latch circuit 10 may be applied to a data memory circuit with set/reset. Alternatively, the latch circuit 10 can be used to construct a memory circuit, such as SRAM. Moreover, although the present embodiment has been showed as a form that used the MOS transistor, the present embodiment is not restricted to this as long as an element has a switching function.
Claims
1. A latch circuit comprising:
- first nodes which are three or more and to which a voltage in a first signal level is set;
- second nodes which are three or more and to which a voltage in a second signal level obtained by inverting the first signal level is set; and
- first node voltage control circuits having said first nodes; and
- second node voltage control circuits having said second nodes,
- wherein each of said first node voltage control circuits is connected with at least two of said three or more second nodes, and controls the voltage of said first node based on the voltages of said at least two second modes, and
- each of said second node voltage control circuits is connected with at least two of said three or more first nodes and controls the voltage of said second node based on the voltages of said at least two first nodes.
2. The latch circuit according to claim 1, wherein said each first node voltage control circuit comprises a first transistor of a first conductive type and a second transistor of a second conductive type whose drains are connected in common to said first node,
- said each second node voltage control circuit comprises a third transistor of the first conductive type and a fourth transistor of the second conductive type, whose drains are connected in common to said second node,
- gates of said first and second transistors are connected with different ones of said three or more second nodes, respectively, and
- gates of said third and fourth transistors are connected with different ones of said three or more first nodes, respectively.
3. The latch circuit according to claim 1, wherein any of said plurality of first node voltage control circuits comprises at least one fifth transistor of the first conductive type which is connected between a source of said first transistor and the first power supply,
- gates of said first transistor, said second transistor, and said fifth transistor are connected with different ones of said three or more second nodes, respectively.
4. The latch circuit according to claim 3, wherein four or more said second nodes are provided,
- any of said plurality of first node voltage control circuits comprises at least one sixth transistor of the second conductive type which is connected in series between a source of said second transistor and the second power supply through a drain and a source of said sixth transistor,
- gates of said firs, second, fifth and sixth transistors are connected with different ones of said four or more second nodes, respectively.
5. The latch circuit according to claim 1, wherein said three or more first nodes are connected with said two or more ones of said plurality of second node voltage control circuits,
- said three or more second nodes are connected with two or more ones of said three or more first node voltage control circuits.
6. The latch circuit according to claim 3, wherein each of said three or more first nodes is connected with a gate of a transistor of the first conductive type which is connected between said first power supply and said second node in each of said at least two second node voltage control circuits, and is connected with a gate of a transistor of the second conductive type which is connected between said second power supply and said second node in each of said at least two second node voltage control circuits,
- each of said three or more second nodes is connected with a gate of a transistor of the second conductive type which is connected between said first power supply and said first node in each of said at least two first node voltage control circuits, and is connected with a gate of a transistor of the second conductive type which is connected between said second power supply and said first node in each of said at least two first node voltage control circuits.
7. The latch circuit according to claim 1, further comprising:
- a plurality of transfer gates connected in correspondence to said three ore more second nodes,
- wherein each of said plurality of transfer gates supplies data to a corresponding one of said three or more second nodes.
8. A flip-flop circuit comprising:
- a clock signal generating circuit configured to supply a clock signal to said two latch circuits,
- a first latch circuit configured to hold a first state corresponding to a first data;
- a second latch circuit configured to hold a second state corresponding to a second data;
- a first transfer circuit connected with said first latch circuit and configured to supply the first data to said first latch circuit in response to said clock signal;
- a second transfer circuit between said first and second latch circuits and configured to transfer the first data from said first latch circuit to said second latch circuit as the second data, and to transfer the second data from said second latch circuit to said first latch circuit as the first data, wherein the second data is obtained by inverting the first data; and
- a third transfer circuit configured to output the second data from said second latch circuit,
- wherein each of said two latch circuits comprises:
- first nodes which are three or more and to which a voltage in a first signal level is set;
- second nodes which are three or more and to which a voltage in a second signal level obtained by inverting the first signal level is set; and
- first node voltage control circuits having said first nodes; and
- second node voltage control circuits having said second nodes,
- wherein each of said first node voltage control circuits is connected with at least two of said three or more second nodes, and controls the voltage of said first node based on the voltages of said at least two second modes, and
- each of said second node voltage control circuits is connected with at least two of said three or more first nodes and controls the voltage of said second node based on the voltages of said at least two first nodes,
- wherein a first one of said two latch circuits function as a latch circuit on an input side in which data is supplied to an input node through a first transfer gate circuit, and a second one thereof functions as a latch circuit on an output side in which the data latched in said input node is outputted, and
- said first node of said latch circuit on the input side is connected with said second node of said latch circuit on the output side through said transfer gate in the latch circuit on the output side.
9. The flip-flop circuit according to claim 8, wherein said each first node voltage control circuit comprises a first transistor of a first conductive type and a second transistor of a second conductive type whose drains are connected in common to said first node,
- said each second node voltage control circuit comprises a third transistor of the first conductive type and a fourth transistor of the second conductive type, whose drains are connected in common to said second node,
- gates of said first and second transistors are connected with different ones of said three or more second nodes, respectively, and
- gates of said third and fourth transistors are connected with different ones of said three or more first nodes, respectively.
10. The flip-flop circuit according to claim 8, wherein any of said plurality of first node voltage control circuits comprises at least one fifth transistor of the first conductive type which is connected between a source of said first transistor and the first power supply,
- gates of said first transistor, said second transistor, and said fifth transistor are connected with different ones of said three or more second nodes, respectively.
11. The flip-flop circuit according to claim 10, wherein four or more said second nodes are provided,
- any of said plurality of first node voltage control circuits comprises at least one sixth transistor of the second conductive type which is connected in series between a source of said second transistor and the second power supply through a drain and a source of said sixth transistor,
- gates of said firs, second, fifth and sixth transistors are connected with different ones of said four or more second nodes, respectively.
12. The flip-flop circuit according to claim 8, wherein said three or more first nodes are connected with said two or more ones of said plurality of second node voltage control circuits,
- said three or more second nodes are connected with two or more ones of said three or more first node voltage control circuits.
13. The flip-flop circuit according to claim 10, wherein each of said three or more first nodes is connected with a gate of a transistor of the first conductive type which is connected between said first power supply and said second node in each of said at least two second node voltage control circuits, and is connected with a gate of a transistor of the second conductive type which is connected between said second power supply and said second node in each of said at least two second node voltage control circuits,
- each of said three or more second nodes is connected with a gate of a transistor of the second conductive type which is connected between said first power supply and said first node in each of said at least two first node voltage control circuits, and is connected with a gate of a transistor of the second conductive type which is connected between said second power supply and said first node in each of said at least two first node voltage control circuits.
14. The flip-flop circuit according to claim 8, further comprising:
- a plurality of transfer gates connected in correspondence to said three ore more second nodes,
- wherein each of said plurality of transfer gates supplies data to a corresponding one of said three or more second nodes.
Type: Application
Filed: Nov 4, 2008
Publication Date: May 14, 2009
Applicant: NEC ELECTRONICS CORPORATION (KANAGAWA)
Inventor: Hiroshi YAMAMOTO (Kanagawa)
Application Number: 12/264,540
International Classification: H03K 3/356 (20060101); H03K 3/00 (20060101);